You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages gafcontinue="Baltaiskauls.png|241" />
  </query-continue>
  <query>
    <pages>
      <page pageid="223" ns="0" title="Bagātais" />
      <page pageid="228" ns="0" title="Bailītis" />
      <page pageid="229" ns="0" title="Bālbārdis" />
      <page pageid="230" ns="0" title="Baldavnieks" />
      <page pageid="231" ns="0" title="Bāliņš" />
      <page pageid="234" ns="0" title="Baļķis" />
      <page pageid="235" ns="0" title="Balodis" />
      <page pageid="239" ns="0" title="Baltābols" />
      <page pageid="240" ns="0" title="Baltais" />
      <page pageid="1686" ns="0" title="Baltacis" />
    </pages>
  </query>
</api>